"'Niceness' -- in the form of agreeableness -- does not appear to pay," the authors conclude starkly.

There are upsides to being nice in the office, such as being better liked by co-workers, the authors say, pointing to a raft of earlier studies.

But the bottom line, according to four studies they conducted, is that "agreeableness is negatively related to income and earnings."

In other words, nice guys earn less.

And the authors do mean guys. They found that men who are nice, in defiance of gender stereotypes, "do take a hit for being highly agreeable," suffering a "backlash" that shows up in their paychecks.

Women, on the other hand, do not appear to get the same benefits men do for being disagreeable.

"Do Nice Guys -- and Gals -- Really Finish Last? The Joint Effects of Sex and Agreeableness on Income," by Timothy A. Judge of the University of Notre Dame, Beth A. Livingston of Cornell University and Charlice Hurst of the University of Western Ontario, is published in the Journal of Personality and Social Psychology.

The findings resonated with workers around the world.

"You have to be ruthless in the corporate world," said Farhana Qaosar of Sydney. "If you have a weak spot or dare to show it, people will take your advantage. That's how it is. You don't succeed because you know more but because you can adapt."

The study made sense to Matt DeFaveri of Cleveland as well, he said.

"A company full of people in agreement would have a hard time establishing or maintaining any kind of hierarchy," he said. "Someone has to differentiate themselves from the pack, and being 'disagreeable' seems like a way to accomplish that. I don't think it's fair to associate disagreeableness with meanness, though."

Jessica Fearnow of Sacramento, California, found the study explained things for her -- and drew some cold comfort from it.

"I was just thinking about how I am not making that much more than I was as an intern" nine years ago, she said. "I guess that makes me a really nice person?"